X-ray systems are very common. They are used with a plurality of applications, amongst others for the angiographic representation of the coronary vessel. In the context of the angiography, different analysis procedures for the acquired images are used. Examples of such analysis procedures are the determination of the flow speed of the blood in the vessels or the determination of the perfusion of the tissue supplied with blood via the vessels. With these two analysis procedures (and also with other analysis procedures) adjustment parameters are manually given to the recording arrangement by an operator of the x-ray system. The operator can provide the position of the source and/or the x-ray detector for example. Furthermore, the operator can provide a frequency and/or a trigger condition for images that can be acquired for example. The user can also provide parameters, which influence the processing of the acquired images. Depending on the given parameter the operator can for example adjust the parameters directly, provide the parameters to a control device, which controls the recording arrangement accordingly, or can provide the parameters of a processing device for the acquired images.
The x-ray source emits x-rays according to the adjustment parameters given manually. In accordance with the manually given adjustment parameters, the x-ray detector likewise respectively acquires a sequence of at least two-dimensional images of an object to be examined. The object to be examined is arranged between the x-ray source and the x-ray detector during the acquisition of the images.
The number of adjustable parameters is very large. With some of the adjustable parameters, a good or even optimal adjustment can also be achieved intuitively. For example the positioning of the x-ray source and the x-ray detector relative to the object to be examined is in many cases—but not always—relatively simple. Nevertheless, with other adjustable parameters, a good adjustment is not easily possible. In particular, the parameters often mutually influence each other. It is therefore difficult to find a good parameter combination.
A further problem consists in that in some cases, with one and the same object to be examined (e.g. with the same human), the same examination is to be carried out over larger temporal intervals. If in such a case, the adjustment parameters, with which the sequence of images is acquired and processed, vary from one examination to another, this can adversely affect the significance of the comparison of the examinations. If it is erroneously assumed that the adjustment parameters are the same, it is even possible for the examinations to be incorrectly evaluated.
A further problem consists in that in many cases more than one optimal parameter combination exists. Instead, objective and subjective factors influence whether a parameter combination is classified as good. An example of an objective factor is the used contrast means and the characteristics of the object to be examined (in particular its thickness). The individual image impression in particular is considered among the subjective factors, which the operator of the x-ray system (or another person, who examines the images) notices. It is therefore not possible to carry out an optimal adjustment of the parameters in advance.